Help wanted solving groove for O ring cutting on lathe

Ok, thank you Hopper, I am on it.

You're welcome. Good luck with the project.

I'am not sure of your experience in cutting plastics. But if you go too fast you will melt the material to the tool. Sometimes it is best to use a narrower tool that is sharp and with the final corner radius detail. For a 5mm section O ring the groove will be about 5.5 mm wide and about 9.3 mm deep on diameter. A tool made that is about 2mm wide and about 5 mm out at that width will work well. When the tool gets too wide, it creates a lot of chatter on the work piece etc.

Neil

Please keep us informed on the progress of your project. Good luck.

Hi Neil, yes I have some experience using Engineering PVC which is a lovely material to work with. You are right, things need to be kept quite slow and small cuts at a time. Sharp tools are a must.

Thanks all, will keep you posted with progress.

This is a picture of the method I suggested. You may gain just enough on the diameter.

Les.

You can easily make a holder like the boring bars that have been shown, bit of round bar drilled through say 1/8" and cross drilled for a M3 grub screw. Then just grind down an old centre drill to make the cutting tool.

Or if you already have something that will cut internal grooves then just mount it upside down and run the lathe backwards

Hi gents

So I have bought the exact same boring bar as shown in Mr Hopper's post... but for the life of me, I can't fathom out how the centre rod stays in position within the square outer jacket.

It has grub screws to keep the tool tight within the rod holes, but how does it stay in position within the outer jacket, anyone?

Sorry to be such a dumbo.

when you clamp it in toolholder it will hold it tight.

The presure from the toolpost screws will close up the square holder, that is why it has a slot in it and that should be positioned to one side.

I thought that, but it still moved?

Are you saying that the square holder has to be slightly off centre, so the tool post screws push down on the grooved part?

That's a cool piece of home made kit JasonB. When I am a little more experienced, I may give that a go. Thanks for the suggestion.

Thanks Les... I see what you mean. I may try that if I the boring bar idea doesn't work.

Why do they place the compound rest so far to the left of the cross slide? What's the rationale?

Hi Christine,
Looking end on to the boring tool the slot in the square part should be a either the 3 oclock or 9 oclock position so that the pressure of the screws can compress the square part. It could be that the opposite side to the slot is too strong for the tool post screws on your lathe to compress the square part enough to grip the bar. If this is the case you could try grindind a groove in the square part on the opposite side to the slot to make it easier to compress.

Les.

Edited By Les Jones 1 on 21/11/2016 20:19:53

Thanks Les. I'll look at it tomorrow and let you know how I get on.

Like this

Ok, got you. Thanks Mr Hopper.